1 Topic by rrssll

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Topic: Figured out why my Z axis jumped so much

The tl;dr version is that there's a little ring in the middle of the z-axis motor that you can tighten.

More detail:

My Z axis was very jumpy when making small movements.  More going down than up. I removed the shroud covering the shaft and found that there's nothing bracing the bottom of the shaft at all. This was pretty surprising. If I put my finger on the end of the shaft while it moved then that damped the vibration a lot. It turns out the z-axis shaft goes all the way through the motor and there's a ring with two holes in it that you can use to turn the ring and tighten the grip on the threaded rod. I happened to have a pair of needle nose pliers that fit as if they were made for the job. I'm not sure what kind of tool is normally used for this.

I've had a lot of good pointers from this forum (mostly things to tighten on the Press) so I thought I'd share in case it helps anyone else.

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2 Reply by thatdecade

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Re: Figured out why my Z axis jumped so much

Found the ring with two holes and tightened clockwise.  No change in bed bounce while descending (backlash).

Some other fixes that have been previously discussed.  Most people add springs.
http://www.soliforum.com/post/82365/#p82365
http://www.thehacksmith.ca/2013/03/soli … grade.html

3 Reply by tomkwc

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Re: Figured out why my Z axis jumped so much

Tightening by rotating those 2 pin holes solved my thumping issue.

Thanks!

4 Reply by rrssll

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Re: Figured out why my Z axis jumped so much

Glad to hear it helped.

@thatdecade - The backlash spring sounds like a nice tweak but I'd imagine the fact that the bottom of the axis is completely free floating in air would make a bigger difference than the nut. That long wobbling rod is basically an amplifier for any vibration that comes from the motor. Still really surprised that it's not secured somehow.

5 Reply by TruFord93

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Re: Figured out why my Z axis jumped so much

I am going to have to look closely at mine but would it be possible to print something to support the rod? My only thoughts would be that youd lose z build area as I can see the lower endstop at the bottom. Can anyone confirm if we could anchor it with little to no loss in z-axis?

6 Reply by slovenian6474

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Re: Figured out why my Z axis jumped so much

Anyone know the thread and size of the lead screw?

7 Reply by slovenian6474 (edited by slovenian6474 2015-02-12 22:27:10)

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Re: Figured out why my Z axis jumped so much

So I stopped printing long enough to look into this a little bit.  Here's some pictures.  The screw is a 8mm (don't really know the pitch.  I'm assuming TR8*8).  The nut that attaches to the bed is nothing fancy.   Just a nut.  Also, with the bed at Z0, there is almost 13mm clearance.
ht tp://i.imgur.com/nyBLYcal.jpg
ht tp://i.imgur.com/yAyWU3Cl.jpg

I wonder if this would be an easy bolt-on fix.  I'll measure the screw pattern when the next print is finished.
robotdigg       /product/18/Anti-backlash-Nut-for-Tr8*8-Leadscrew

Sorry about potato shots and can't post links.

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